The compacting machines operating by their own weight (static weight) have their weight increased by the addition of water, sand or scrap in spaces defined inside the compacting cylinders or rollers, or also inside the chassis, which is constructed in order to define a reservoir in the space existing between the front and rear wheel-axle assemblies.
These known ballast systems require the handling of bulk materials and do not allow the easy control or adjustment of the mass of the material supplied to the ballast spaces, in order to adapt the weight of the compacting machine to the needs of the operation to be carried out. In these prior art solutions, the ballast control requires the use of a scale, which is hardly ever available in the working yard.
Besides the inconvenience cited above, the density of the bulk material fed into the ballast reservoirs or spaces requires the creation of considerable volumes in the equipment design, so as to accommodate the necessary amount of ballast material.
Another inconvenience of the known technical solutions results from the fact that the difficulties for charging and removing the bulk materials usually avoid the adjustment of the equipment, in terms of ground load, to the ideal conditions of each application and of the material to be compacted.
In the particular case of the wheeled compacting machines, the load per wheel is a determinant factor for obtaining a desired compacting level, because it directly influences the pressure value resulting from the contact of the tire with the material to be compacted.
It should also be observed that the space, which is necessary for providing the usual ballast of humid sand, avoids the achievement of high loads per wheel and therefore limits the compacting capacity of the equipment. In general, the most common wheeled compacting machines provide a load per wheel from about 3,000 Kg to about 3,500 Kg. Nevertheless, it has been more and more frequent the need for compacting applications requiring a load per wheel of about 4,000 Kg, which load has been obtained up to now only through very heavy equipments, which are very costly and with limitations concerning transportation, visibility and maneuverability.